Method and system for installing a tubular element in a borehole

ABSTRACT

A radially expandable tubular element ( 1 ) is installed in an underground borehole by:—lowering the tubular element ( 1 ) into the borehole a work string ( 2 ) and an anchor tool ( 16 ) to which the tubular element ( 1 ) is connected via a dimple connection ( 32 ) to increase the weight carrying capacity of the anchor tool ( 16 );—connecting an expander ( 14 ) to the work string ( 2 ) at a position below the anchor tool ( 16 ); and—radially expanding the tubular element ( 1 ) by pulling the expander ( 14 ) on the work string ( 2 ) through the tubular element ( 1 ).

The present invention relates to a system and a method for installing atubular element in a borehole extending into an earth formation

Wellbores for the production of hydrocarbon fluid generally are providedwith steel casings and/or liners to provide stability to the wellborewall and to prevent undesired flow of fluid between the wellbore and thesurrounding earth formation. A casing generally extends from surfaceinto the wellbore, whereas a liner may extend only a lower portion ofthe wellbore. However in the present description the terms “casing” and“liner” are used interchangeably and without such intended difference.

In a conventional wellbore, the wellbore is drilled in sections wherebyeach section is drilled using a drill string that has to be lowered intothe wellbore through a previously installed casing. In view thereof thewellbore and the subsequent casing sections decrease in diameter withdepth. The production zone of the wellbore therefore has a relativelysmall diameter in comparison to the upper portion of the wellbore. Inview thereof it has been proposed to drill a “mono diameter” wellborewhereby the casing or liner to be installed is radially expanded in thewellbore after lowering to the required depth. Subsequent wellboresections may therefore be drilled at a diameter larger than in theconventional wellbore. If each casing section is expanded to the samediameter as the previous section, the wellbore diameter may remainsubstantially constant with depth.

US-2006/0065403-A1 discloses an assembly for expanding a tubular elementin a wellbore, whereby the tubular element is suspended duringrunning-in into the wellbore on a work string having an expander at itslower end, and whereby the tubular element passes through an existingcasing in the wellbore. There is a risk that the lower end of thetubular element is prematurely expanded by the expander, for example ifthe weight of the tubular element causes the tubular element to slipdownward relative to the work string. Such unintended expansion mayhamper, or prevent, lowering of the tubular element through the existingcasing.

Other prior art anchoring systems are known from US patent applications2007/000669; 2008/041596 and 2006/196654 and International patentapplication WO/196654, which have the risk that the tubular elementunintentially slips down and is prematurely released from the workstring.

It is an object of the invention to provide an improved method andsystem for installing a tubular element in a borehole extending into anearth formation, which overcome or alleviate drawbacks of the prior art.

The invention provides a method of installing a radially expandabletubular element in an underground borehole comprising the steps of:

(a) positioning in the tubular element an anchor tool having acylindrical outer surface provided with at least one dimple;

(b) operating a pressing device to press a respective wall portion ofthe tubular element into the at least one dimple to create a dimpleconnection between the tubular element and the anchor tool;

(c) providing a work string connected to the anchor tool;

(d) operating a drive device to lower the tubular element into theborehole on the work string when the tubular element is connected to theanchor tool via the dimple connection;

(e) connecting an expander to the work string at a position below theanchor tool; and

(f) radially expanding the tubular element by pulling the expander onthe work string through the tubular element.

The invention also provides a system for installing a radiallyexpandable tubular element in an underground borehole, the systemcomprising:

(a) an anchor tool adapted to be positioned in the tubular element andhaving a cylindrical outer surface provided with at least one dimple;

(b) a pressing device for pressing a respective wall portion of thetubular element opposite the at least one dimple into the dimple, tocreate a dimple connection between the tubular element and the anchortool;

(c) a work string connected to the anchor tool;

(d) a drive device for lowering the tubular element into the borehole onthe work string when the tubular element is connected to the anchor toolvia the dimple connection;

(e) means for connecting an expander to the work string at a positionbelow the anchor tool; and

(f) means for radially expanding the tubular element by pulling theexpander on the work string through the tubular element.

According to the method and system of the invention, the weight carryingcapacity of the work string is increased by virtue of the dimpleconnection between the tubular element and the anchor tool. The dimpleconnection carries at least a portion of the weight of the tubularelement during installation in the borehole. Furthermore, the dimpleconnection may be released easily by pulling up the work string, orpushing down the work string, through the tubular element afterinstallation in the borehole whereby each wall portion is deformed backto substantially the original shape.

Suitably, each dimple has first and second surfaces arranged oppositeeach other and extending in circumferential direction of the anchortool, said surfaces having mutually different inclination anglesrelative to the cylindrical outer surface. It is thereby achieved thatthe dimple connection has a high load carrying capacity in one axialdirection and may be released easily in the other axial direction. Forexample, the first surface may extend at an inclination angle α1 and thesecond surface at an inclination angle α2 relative to the cylindricalouter surface, the first surface facing upwardly in the borehole, andwherein α1>α2. Furthermore, the dimple connection may be released moreeasily if a rounded transition surface extends between the secondsurface and the cylindrical outer surface.

Suitably the dimple has a bottom surface located between said first andsecond surfaces, the bottom surface extending substantially parallel toa longitudinal axis of the anchor tool. To increase the torquetransmission capacity of the dimple connection the bottom surface mayhave a truncated V-shape.

The cylindrical outer surface of the anchor tool is advantageouslyprovided with a plurality of said dimples spaced in circumferentialdirection of the anchor tool.

Suitably the pressing device includes a die member having an end portionwith a shape similar to the shape of the dimple. To accurately positionthe die member relative to the anchor tool, the pressing device maycomprise positioning means connectable to the anchor tool and adapted tomove the anchor tool relative to the die member so that the dimple islocated opposite the die member.

In an embodiment, the tubular element is a radially expandable tubularelement and the system further comprises an expander for radiallyexpanding the tubular element by axially moving the expander through thetubular element, the expander being connected to the work string at aposition below the anchor tool.

The anchor tool may be released from the tubular element by inducing thedrive device to move the work string in axial and/or rotationaldirection relative to the tubular element so as to deform each said wallportion to a shape substantially similar to the shape of the wallportion prior to step (2) of the method.

The invention will be described hereinafter in more detail and by way ofexample with reference to the accompanying schematic drawings in which:

FIG. 1 shows an exemplary embodiment of the system of the invention,partially in longitudinal section;

FIG. 2 shows a lower portion of an expansion string of the exemplaryembodiment, partially in longitudinal section;

FIG. 3 shows an anchor tool of the exemplary embodiment;

FIG. 4 shows cross-section 4-4 of FIG. 3;

FIG. 5 shows a pressing device used with the exemplary embodiment;

FIG. 6 shows a perspective view of a die member of the pressing device;

FIG. 7 shows the die member after pressing a wall portion of the tubularelement into a dimple of the anchor tool; and

FIG. 8 shows an alternative die member.

In the detailed description and the figures, like reference numeralsrelate to like components.

FIGS. 1 and 2 show an assembly including a tubular element 1 adapted tobe radially expanded in a wellbore (not shown) and a work string in theform of expansion string 2 for radially expanding the tubular element inthe wellbore. The expansion string 2 includes from bottom to top: amandrel 4, a far-cone centralizer 6, a debris catcher 7 and an on-offsub 8 having lower and upper parts 8 a, 8 b. The on-off sub 8 connectsthe expansion string to the lower end of a drill pipe 10 and is adaptedto be disconnected by rotation of the drill pipe 10 relative to themandrel 4.

The mandrel 4 is provided with, from bottom to top: a lock nut 12, anexpander in the form of expansion cone 14, an anchor tool 16 and anear-cone centralizer 18. The expansion cone 14, the anchor tool 16 andthe near-cone centralizer 18 have respective central passages 19, 20, 21through which the mandrel 4 extends. The mandrel can slide through thepassages 19 to 21.

The lock nut 12 is screwed to the mandrel 4 so as to lock the assemblyof expansion cone 14, anchor tool 16 and near-cone centralizer 18 inplace whereby the near-cone centralizer abuts against a shoulder 22 ofthe mandrel 4. Furthermore, the expansion cone 14 is rotationally lockedto the anchor tool 16 by a castellated connection 24, the anchor tool 16is rotationally locked to the near-cone centralizer 18 by a castellatedconnection 25, and the near-cone centralizer 18 is rotationally lockedto the shoulder 22 of mandrel 4 by a castellated connection 26.

Alternatively the anchor tool 16 may be directly rotationally locked tothe mandrel 4 by means of key slots formed in the anchor tool 16 andmandrel 4, with keys fitting in such key slots. This way the castellatedconnections 24, 25 may be eliminated.

The expansion cone 14 has a nose portion of diameter substantially equalto the inner diameter of the unexpanded tubular element 1. The diameterof the expansion cone 14 gradually increases from the nose portion indownward direction to a diameter corresponding to a desired expansionratio of the tubular element 1. The nose portion is provided with anannular seal 28 of resilient material. Furthermore the tubular element 1has an outwardly flaring end section 29 adapted to receive the expansioncone 14, with the largest outer diameter of the end section 29 beingless than, or equal to, the largest outer diameter of the expansion cone14.

The anchor tool 16 has a cylindrical outer surface 30 of diametricalsize allowing the anchor tool 16 to snugly fit into the tubular element1. A plurality of dimples 32 are formed in the cylindrical outer surface30, the dimples being regularly spaced along the circumference of theanchor tool. At each dimple 32, a corresponding wall portion 34 of thetubular element 1 extends into the dimple 32 so as to axially androtationally lock the anchor tool to the tubular element.

FIGS. 3, 4 show the anchor tool 16 in more detail. Each dimple 32 hasfirst and second surfaces 35 a, 35 b oppositely arranged and extendingin circumferential direction of the anchor tool. The surfaces 35 a, 35 bare inclined relative to the cylindrical outer surface 33 at respectiveinclination angles α1, α2. A bottom surface 36 is located between thefirst and second surfaces 35 a, 35 b, which bottom surface extendssubstantially parallel to a longitudinal axis 37 of the anchor tool.Rounded surface portions 38 a, 38 b extend at the transition between thecylindrical outer surface 33 and the respective first and secondsurfaces 35 a, 35 b. The surface portions 38 a, 38 b have roundingradius R.

FIGS. 5 to 7 show a pressing device 40 for pressing, at each dimple 32,the respective wall portion 34 of the tubular element 1 into the dimple32 so as to create a dimple connection between the tubular element 1 andthe anchor tool 16. The pressing device 40 comprises a housing 44 havinga longitudinal bore 46 into which a lower section 47 of the tubularelement 1 snugly fits. The pressing device 40 further comprises a diemember 48 positioned in a radial bore 49 of the housing 44 in slidablemanner. The die member 48 has an end portion 50 facing the tubularelement 1, with inclined surfaces 52 a, 52 b and bottom surface 52 c soas to have a shape similar to the shape of the dimple 32. The anchortool 16 is arranged inside the tubular element 1 whereby the dimple 32is positioned opposite the end portion 50 of die member 48. The pressingdevice 40 optionally further comprises a positioning assembly includinga plate 53 and a cylinder 54 to be arranged inside the anchor tool 16.The cylinder 54 may be axially and rotationally locked to the anchortool 16 by a flange abutting one end of the anchor tool and bolts 56interconnecting the cylinder 54 and the plate 53.

FIG. 8 shows a die member 60 that is largely similar to the die member48, except that inclined surfaces 52 a, 52 b do not extend parallel toeach other so that bottom surface 52 c has a truncated V-shape.

During normal operation the anchor tool 16 is inserted into the lowertubular section 47, and the assembly is then arranged in thelongitudinal bore 46 of the pressing device 40 whereby it is ensuredthat the bottom surface 36 of the dimple is parallel to, and in linewith, the bottom surface 52 c of the die member 48. Optionally thecylinder 54, plate 53 and bolts 56 may be used to accurately positionthe anchor tool 16 so that the dimple 32 is exactly opposite the diemember 48.

The pressing device 40 is then operated to induce die member 48 to pressthe wall portion 34 of the tubular element into the dimple 32 until theinside of the wall portion 34 contacts the bottom surface 36 of thedimple. This procedure is repeated for all dimples 32 whereby each timethe tubular element 1 with the anchor tool 16 inside is rotated relativeto the pressing device so as to position the next dimple 32 opposite thedie member 48. In this manner a dimple connection is obtained betweenthe lower tubular section 47 and the anchor tool 16. Any suitable powersource may be used to operate the pressing device, for example hydraulicpower, electrical power or mechanical power. In a next step the lowertubular section 47 is removed from the pressing device 40 and thepositing assembly, if used, is removed from the anchor tool 16.

The near-cone centralizer 18 is then fitted to the mandrel 4 so that thenear-cone centralizer 18 abuts against shoulder 22 and is rotationallylocked to the mandrel 4 by castellated connection 26. Then the anchortool 16, with the lower tubular section 47 connected thereto, is fittedto the mandrel 4 until the anchor tool abuts the near-cone centralizer.Subsequently the expansion cone 14 is fitted to the mandrel 4 until thenose portion of the expansion cone 14 abuts the anchor tool 16. Then thelock nut 12 is screwed to the mandrel 4 so as to axially lock theexpansion cone 14, the anchor tool 16 and the near-cone centralizer 18to the mandrel 4. The mandrel 4 is then connected to the far-conecentralizer 6, the debris catcher 7 and to the lower end of drill pipe10 via on-off sub 8 as shown in FIG. 1.

Subsequently the assembly is run into the wellbore whereby drill pipesare added to form the expansion string 2, and tubular joints are addedto form the tubular element 1 in correspondence with the depth oflowering.

During running-in the assembly into the wellbore the weight of thetubular element 1 is transferred to the expansion string 2 via thedimple connection between the anchor tool 16 and the lower tubularsection 47, and via the contact between the outwardly flaring endsection 29 of tubular element 1 and the expansion cone 14. Rotary torquerequired for making-up the on-off sub 8, or for reaming the wellborewhile running-in is transferred from the mandrel 4 via the castellatedconnection 26 to the near-cone centralizer 18, then via the castellatedconnection 25 to the anchor tool 16, and then via the dimple connectionto the tubular element 1.

If the tubular element needs to be pushed in downward direction toovercome friction between the tubular element 1 and the wellbore wall,for example in an inclined borehole section, the required downward forceis also transmitted to the tubular element via the dimple connection.

After the tubular element 1 has reached the target depth in thewellbore, the dimple connection between anchor tool 16 and tubularelement 1 is released. This may be done by moving the expansion string 2upward or downward while the tubular element 1 is kept stationary in thewellbore. In this manner each wall portion 34 of the tubular element ismoved out of the respective dimple 32 whereby the wall portion issubjected to plastic and/or elastic deformation. Such deformation isfacilitated by the inclined surfaces 35 a, 35 b and the rounded surfaceportions 38 a, 38 b. Generally, the dimple connection is released moreeasily for smaller inclination angles α1 and α2 and/or for larger valuesof R. Instead of, or in addition to, releasing the dimple connection byaxial movement of the expansion string 2 relative the tubular element 1,the dimple connection may be released by rotating the expansion string 2relative the tubular element 1.

In the present example the inclination angles α1 and α2 are equal.However the surfaces 35, 35 b may have different inclination angles. Forexample, since surface 35 a must carry a relatively large portion of theweight of the tubular element 1 during lowering into the wellbore, angleα1 may be selected larger than angle α2 in order to increase the loadcarrying capacity of surface 35 a. In such application the inclinationangle α2 is relatively small, therefore the dimple connection may bereleased relatively easy by moving the expansion string 2 downward whilethe tubular element 1 is kept stationary.

Once the dimple connection is released, radial expansion of the tubularelement 1 is started by pulling the expansion string 2 upwardly throughthe tubular element.

If the expansion cone 14 gets stuck in the tubular element 1 during theexpansion process, for example with the expansion cone in a section ofoverlap of the tubular element 1 with another tubular element, the drillpipe has to be disconnected from the expansion string 2 by breaking outthe on-off sub 8. The required break-out torque is transmitted from thedrill pipe 10 via the on-off sub 8 to the mandrel 4, then via thecastellated connections 26, 25, 24 to the expansion cone 14, and finallyvia the face of the expansion cone 14 to the tubular element 1.

The load carrying capacity of the dimple connection is selected suchthat the force required to release the dimple connection by upwardmovement of the anchor tool relative to the tubular element exceeds thebuoyant weight of the tubular element in a vertical borehole. In thismanner premature plastic deformation of the tubular element isprevented.

Instead of the tubular shaped anchor tool 16 described above, the anchortool may be formed as a massive cylinder that is integrally formed withthe mandrel 4 or connected to the mandrel in any suitable manner.

Design parameters for the anchor tool may be based on the dimple lengthL, depth D, angle α1 and/or α2 and round-off radius R (FIG. 4). Forexample, axial load capacity may be increased by providing more dimples,increasing α1 and/or α2, or increasing depth D. Torsional load capacitymay be increased by providing more dimples, increasing length L,increasing depth D or using a dimple with a V-shaped bottom surface(FIG. 8). Release forces required to release the dimple connection maybe reduced by less dimples, improved lubrication, decreased α1 and/or α2or lower depth D. Galling between the anchor tool and the tubularelement may be mitigated by increasing the round-off radius R.Furthermore, a relatively sharp angle α1 may increase the weightcarrying capacity and a relatively low angle α2 may reduce the releaseforce of the dimple connection.

The present invention is not limited to the embodiments as describedabove, wherein various modifications are conceivable within the scope ofthe appended claims. Features of different embodiments may for instancebe combined.

1. A method of installing a radially expandable tubular element in anunderground borehole comprises the steps of: (a) positioning in thetubular element an anchor tool having a cylindrical outer surfaceprovided with at least one dimple; (b) operating a pressing device topress a respective wall portion of the tubular element into the at leastone dimple to create a dimple connection between the tubular element andthe anchor tool; (c) providing a work string connected to the anchortool; (d) operating a drive device to lower the tubular element into theborehole on the work string when the tubular element is connected to theanchor tool via the dimple connection; (e) connecting an expander to thework string at a position below the anchor tool; and (f) radiallyexpanding the tubular element by pulling the expander on the work stringthrough the tubular element.
 2. The method of claim 1, wherein the stepof operating the pressing device comprises pressing a die member againstsaid wall portion of the tubular element, the die member having an endportion with a shape similar to the shape of the dimple.
 3. The methodof claim 1, further comprising releasing the anchor tool from thetubular element by inducing the drive device to move the work string inat least one of axial and rotational direction relative to the tubularelement to deform each said wall portion to a shape substantiallysimilar to the shape of the wall portion prior to the step of operatingthe pressing device.
 4. A system for installing a radially expandabletubular element in an underground borehole, the system comprising: (a)an anchor tool adapted to be positioned in the tubular element andhaving a cylindrical outer surface provided with at least one dimple;(b) a pressing device for pressing a respective wall portion of thetubular element opposite the at least one dimple into the dimple, tocreate a dimple connection between the tubular element and the anchortool; (c) a work string connected to the anchor tool; (d) a drive devicefor lowering the tubular element into the borehole on the work stringwhen the tubular element is connected to the anchor tool via the dimpleconnection; (e) means for connecting an expander to the work string at aposition below the anchor tool; and (f) means for radially expanding thetubular element by pulling the expander on the work string through thetubular element.
 5. The system of claim 4, wherein the at least onedimple has a first surface and a second surface arranged opposite eachother and extending in circumferential direction of the anchor tool,said first and second surfaces having mutually different inclinationangles relative to the cylindrical outer surface.
 6. The system of claim5, wherein the first surface extends at an inclination angle α1 and thesecond surface at an inclination angle α2 relative to the cylindricalouter surface, the first surface facing upwardly in the borehole.
 7. Thesystem of claim 6, wherein α1>α2.
 8. The system of claim 6, wherein arounded transition surface extends between the second surface and thecylindrical outer surface.
 9. The system of claim 5, wherein the dimplehas a bottom surface located between the first surface and the secondsurface, the bottom surface extending substantially parallel to alongitudinal axis of the anchor tool.
 10. The system of claim 9, whereinthe bottom surface has a truncated V-shape.
 11. The system of claim 4,wherein the cylindrical outer surface of the anchor tool is providedwith a plurality of said dimples spaced in circumferential direction ofthe anchor tool.
 12. The system of claim 4, wherein the pressing deviceincludes a die member having an end portion with a shape similar to theshape of the dimple.
 13. The system of claim 12, wherein the pressingdevice comprises positioning means connectable to the anchor tool andadapted to move the anchor tool relative to the die member so that thedimple is located opposite the die member.
 14. The system of claim 4,wherein the tubular element is a radially expandable tubular element,and wherein the system further comprises an expander for radiallyexpanding the tubular element by axially moving the expander through thetubular element, the expander being connected to the work string at aposition below the anchor tool.